The external split-worker ingest pods (MCP_ROLE=worker / procrastinate) had
no observability: the worker CLI entrypoint never started a Prometheus
metrics server and never configured structured logging, so the pods that do
the real parse/embed/upsert work were invisible to Prometheus and emitted
plain-text logs the platform pipeline couldn't parse.
The always-on API pod bootstraps observability in its lifespan (app.py), but
the worker has its own entrypoint and never went through that path (or
uvicorn's JSON log_config). Add `_init_worker_observability()` mirroring the
API pod: setup_logging (JSON), setup_metrics on METRICS_PORT when
METRICS_ENABLED, and setup_tracing when an OTLP endpoint is configured.
Runs after the INGEST_QUEUE=postgres check so a misconfigured worker fails
fast without binding a metrics port.
This also unblocks the document-pipeline observability shipped in #831
(Deck #175): the astrolabe_* parse/embed/chunk metrics and the
document_processor.parse span are recorded in the shared registry/processor
code the worker executes — they were simply never exposed in external mode
because the worker served no /metrics and set up no tracer.
Deck #310, unblocks #175.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
